This thread is just silly. There is no reason whatsoever for a 24-70/2.8 IS to have or need a larger front element than a 24-70/2.8 non-IS.

Also, some of the posts give the impression that a front elelement over 90mm is a done deal and build further on that soft-cheese foundation. I think the 72mm, 77mm, and 82mm filters (and the legacy smaller sizes) will be the consumer L lens range for many years to come.

A google search led me back here to another post mentioning the 24-70 and a 95mm filter size. OP was the same that mentioned it in the other thread. Not sure where the info is from. Radiating, where did you hear about the 95mm filter size?

I've never heard that one either, but a larger front element would boost the price a lot for a relatively small difference in size, perhaps even double the price. Those large lens elements ground to less than a millionth of a inch accuracy get insanely expensive as they get larger. The cost of a larger filter would only be a few hundred dollars.

I personally still don't see the usefulness of IS on a lens like that and I personally would always chose the non-IS version over the IS. It's really more an amateur gadget unless were talking much longer focal lengths.

You may have steadier hands than average. I certainly don't have a case of the "trembles" but do achieve a clear benefit from IS on my 24-105 f/4is and of course the 70-200 f/2.8isII. A 24-70 f/2.8is would be a very useful bit if kit for me. I just ache for IS on my 135 f/2.

Some people have the gift of steady hands. For the rest of us, IS = more keepers.

A google search led me back here to another post mentioning the 24-70 and a 95mm filter size. OP was the same that mentioned it in the other thread. Not sure where the info is from. Radiating, where did you hear about the 95mm filter size?

Canon experimented with 2 different possible image stabilized f/2.8 zooms. There are patents for them available on both *********.com and egami.com, and canonrumors.com

The first of these two lenses is a 28-70mm f/2.8 IS, with a filter size of 86mm. The second was a 24-70mm f/2.8 IS with a filter size of 95mm, (although it could have used 90mm filters, if anyone made those).

The 24-70mm II uses I beleive (don't quote me on the precise number) a 68mm front element with an 82mm filter size. The 24-70mm f/2.8 IS used a 77.29mm front element!

Other sources, such as Canonrumors themselves do add that it's not strictly the sheer size of the lens that was an issue (or it's resulting filter size) but that as a result of it's size it also weighed a ton and the lens elements were expensive due to their size. Though this thread is focusing more on the filter size issue being serious enough to be partly responsible for killing a lens, and if that's justified. I'm sure there are tons of other threads that cover whether the size and weight of a lens are an issue people care about.

A google search led me back here to another post mentioning the 24-70 and a 95mm filter size. OP was the same that mentioned it in the other thread. Not sure where the info is from. Radiating, where did you hear about the 95mm filter size?

Canon experimented with 2 different possible image stabilized f/2.8 zooms. There are patents for them available on both *********.com and egami.com, and canonrumors.com

The first of these two lenses is a 28-70mm f/2.8 IS, with a filter size of 86mm. The second was a 24-70mm f/2.8 IS with a filter size of 95mm, (although it could have used 90mm filters, if anyone made those).

The 24-70mm II uses I beleive (don't quote me on the precise number) a 68mm front element with an 82mm filter size. The 24-70mm f/2.8 IS used a 77.29mm front element!

Other sources, such as Canonrumors themselves do add that it's not strictly the sheer size of the lens that was an issue (or it's resulting filter size) but that as a result of it's size it also weighed a ton and the lens elements were expensive due to their size. Though this thread is focusing more on the filter size issue being serious enough to be partly responsible for killing a lens, and if that's justified. I'm sure there are tons of other threads that cover whether the size and weight of a lens are an issue people care about.

Just did a search on the USPTO/google patent and there are no patents for anything related to a 24-70 f/2.8 IS. Loads of references to the 24-70 f/2.8 MKII and 24-70 f/4 IS. It could not be published yet, but I want to see the source material from the websites as nothing shows up in searching on them.

What do facts have to do with anything, people don't want facts interfering with their opinions.

Most people of course are open to interfering facts - but in my experience it is often discovered that these facts, after due inspection, either aren't really proven/applicable or even magically validate the seemingly contradicting opinion as the exception to the rule :-p

The 24-70mm II uses I beleive (don't quote me on the precise number) a 68mm front element with an 82mm filter size. The 24-70mm f/2.8 IS used a 77.29mm front element!

So in simple layman's terms a Canon 24-70/2.8IS needs larger glass elements to be sharper than the 82mm Tamron 24-70vc, or does the Canon IS have another construction that is larger than Tamron VC?

I have to admit I don't quite understand it yet because I imagined the IS being build *around* the lens, but now it seems like the IS needs some glass "headroom", at least in the front element, to work because the angle of the lens changes slightly when IS is at work?